My very busy week ended with a seminar on Gaussian Processes, that I gave on the blackboard, supported with some projected slides showing Foreman-Mackey's demo plots. I tried to go slowly, but there is a lot to do in a one-hour lecture on something that can fill an entire semester's course. I got great questions from the crowd.
In the morning, Željko Ivezić (UW) and I discussed LSST cadence and exposure-time issues. He showed me his "conservation laws" slide, which shows that the exposure time flows down to all sorts of constraints on the survey. We talked about the plan to split the individual (probably 30-sec) exposures into two parts. What's the difference between 15+15 and 5+25 (and so on)? The expectations about the noise and the point-spread function are both related to the exposure time, and there are cosmic rays and moving objects. We tried to spec out some simple projects to analyze the relevant problems. Simplest: What are the implications for point-source position and flux measurements, in the limit that the sky is static? Even this question is not trivial.